Private IP Addresses
Private IP addresses are ranges of IP addresses that are set aside for private use. IP addresses within these ranges are non routable on the internet. This means they cannot be reached via the internet. Private IP addresses are used on private subnets (eg. a home or business network). The reason for using a private IP address range is so there will never be a clash with a 'real' or public IP address. If you had a home network with IP addresses from the public range (that weren't assigned to you), you wouldn't be able to access any websites that happened to be using the same IP addresses. This is because your local router will route your request back to the local network.
The following IP address ranges are set aside for private use:
| IP Range | Start Address | End Address | Number of Addresses |
|---|---|---|---|
| 10.0.0.0/8 | 10.0.0.0 | 10.255.255.255 | 16,777,216 |
| 172.16.0.0/12 | 172.16.0.0 | 172.31.255.255 | 1,048,576 |
| 192.168.0.0/16 | 192.168.0.0 | 192.168.255.255 | 65,536 |
Private network addresses are allocated in RFC1918 - Address Allocation for Private Internets.